You need to careful while changing your blogger template.
Backup your blogger template.
Following are the steps
1. Login To blogspot.com
2. Go you your site click on edit html
4. Press Ctrl+F and search for ]]></b:skin> and then above it just paste the following CSS code.
#navbar { height: 0px; visibility: hidden; display: none;}
#navbar-iframe { height: 0px; visibility: hidden; display: none;}
5. Now save the template and your work done.
